Chemical injection valve

ABSTRACT

An improved surface controlled chemical injection valve and method for injecting chemical fluid into the bore of a tubing string of a well are provided, the chemical injection valve having at least one piston movable in response to the pressure of the chemical fluid, an actuator connected to the piston, and a flow restrictor wherein the pressure of the chemical fluid supplied to the valve from the chemical fluid source acts on the piston to cause the actuator to open the valve and inject the chemical fluid into the tubing string bore. The flow restrictor is mounted downstream of the piston to create sufficient available pressure in the chemical fluid upstream of the flow restrictor to act on the piston and hold the valve in the open position.

FIELD OF THE INVENTION

This invention relates to an improved chemical injection valve and animproved method for injecting chemical fluid into the bore of a tubingstring of a well. In particular, the invention pertains to a method andapparatus for opening and holding open a chemical injection valve byproviding a flow restrictor downstream of a piston for activating thevalve.

BACKGROUND OF THE INVENTION

Chemical injection valves are used to inject chemical fluids such ascorrosion inhibitors, solvents, and other chemicals into the producedfluid in the bore of a tubing string of a well. The chemical fluidsinhibit and alleviate corrosion of the tubing string and crystallizationand subsequent deposition of paraffins, sulfates, and the like from theproduction fluid. Commercially available chemical injection valves, suchas that shown in FIG. 1, typically use a spring operated ball-and-seattype of valve closure arrangement. In such a valve, chemical fluid issupplied to the valve from a surface source, and once inside the valve,the pressure of the chemical fluid urges the valve ball away from theseat. However, a spring exerts an opposing force on a valve followerwhich urges the valve ball to the seat. Therefore, to open the valve,the pressure of the chemical fluid must be greater than the opposingspring force plus the pressure in the tubing string bore. And to closethe valve, the pressure of the chemical fluid must be less than theopposing spring force.

The problem with this type of chemical injection valve is that the valveball and seat are constantly in the flow path of the chemical fluid andare therefore subject to the corresponding negative effects of the flowsuch as scale build up, deposits, and flow cutting. As a result of thesenegative effects, the valve ball may not seal tightly against the seat,and if the pressure in the bore of the tubing string is less than thepressure in the supply conduit, injection of chemical fluid into thetubing string bore will continue until the pressure equalizes across thevalve. In addition, a surge of pressure in the tubing string bore mayforce production fluid through the valve and into the supply conduit.

SUMMARY

Applicants provide an improved valve and method for injecting chemicalfluid from a chemical fluid source into the bore of a tubing string of awell. The improved valve has a housing which includes a flow passagetherein for communicating with the tubing string bore and an openingtherethrough communicating with the flow passage and the chemical fluidsource. The valve may be mounted in a mandrel in the tubing string boreat a pre-selected location downhole. A valve closure is connected to thehousing and is movable from a closed position to an open position. Meansfor urging the valve closure to its closed position, such as a spring,are included. When in its closed position, the valve closure is adaptedto block flow of produced fluid from the tubing string bore into theflow passage of the valve. When the valve closure is in its openposition, the valve is open and chemical fluid may be injected into thetubing string bore. An actuator for opening the valve closure is locatedin the housing. The actuator is movable from a first position, in whichthe valve closure is closed, to a second position, in which the valveclosure is open, thereby permitting chemical fluid to flow through theflow passage into the tubing string bore. A flow restrictor in the flowpassage restricts flow of the chemical fluid through the flow passageand thereby creates a pressure differential across the flow restrictor.At least one piston movably mounted in the housing is connected to theactuator and is in communication with the chemical fluid source upstreamof the flow restrictor. The piston is adapted to move the actuator fromits first position to its second position, wherein the valve closure isopen, in response to the pressure of the chemical fluid upstream of theflow restrictor.

Operation of the valve is as follows. When chemical fluid is supplied tothe valve from the chemical fluid source, the pressure of the chemicalfluid acts on the piston which causes the actuator to move the valveclosure to its open position, to open the valve and inject chemicalfluid into the tubing string bore. Without a flow restrictor, thepressure of the chemical fluid upstream of the flow restrictor willdecrease when the valve is opened and the chemical fluid is injectedinto the tubing string bore. However, the flow restrictor creates apressure differential across the flow restrictor which results insufficient available pressure in the chemical fluid upstream of the flowrestrictor to cause the piston to hold the valve open. When the valveclosure is in its open position, the actuator is designed to shield thevalve closure from the chemical fluid, and as a result, to preventerosion or damage to the valve closure so the valve closure will have atighter and more reliable seal and the valve will have a tighter andmore reliable shutoff.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a conventional chemical injection valvehaving a spring operated ball-and-seat type of valve closurearrangement.

FIG. 2 is an illustration of a chemical injection valve which is mountedin a side pocket mandrel in the tubing string of a well.

FIG. 3 is a cross sectional partial view of the chemical injection valveof the invention in which the valve is closed and the flow restrictor islocated downstream of the valve closure.

FIG. 4 is a cross sectional partial view of the chemical injection valveof the invention in which the valve is open and the flow restrictor islocated downstream of the valve closure.

FIG. 5 is a cross sectional partial view of the chemical injection valveof the invention in which the valve is closed and the flow restrictor isconnected to the actuator.

FIG. 6 is a cross sectional partial view of the chemical injection valveof the invention in which the valve is open and the flow restrictor isconnected to the actuator.

FIG. 7 is a cross sectional partial view of the chemical injection valveof the invention taken along line 7--7 of FIGS. 4 and 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 3 and 4, the reference numeral 10 generally indicatesa preferred embodiment of the chemical injection valve of the presentinvention. The chemical injection valve 10 has a housing 12 including aflow passage 14 therein for defining the flow path of the chemical fluidand for communicating with the tubing string bore. The housing 12 isgenerally tubular and is adapted to be mounted to lock and set in amandrel in the tubing string bore, as is shown in FIG. 2. It is notnecessary to the invention that the housing be tubular. Any othersuitable housings may be used. The flow passage 14 has a closed end 16,such as a threaded plug, for blocking flow of chemical fluid to thetubing string bore and an open end 18 communicating with the tubingstring bore. The housing 12 also includes an opening 20 therethroughcommunicating with the flow passage 14 and the chemical fluid sourcewhich is located on the surface (not shown). Preferably, chemical fluidis introduced into the tubing-casing annulus for direct entry into thevalve 10 through the opening in the housing 20. However, chemical fluidmay be supplied to the valve 10 through a small diameter tubing (notshown) that passes from the chemical fluid source on the surface intothe tubing-casing annulus and is connected to the injection mandrel andis in communication with the opening in the housing 20 in any suitablemanner. Any other suitable means for supplying the chemical fluid to theopening in the housing 20 could be used. Referring to FIG. 3, packing 47prevents production fluids from entering the opening 49 through thehousing 12. As is known to those skilled in the art, a housing 12 whichdoes not include the opening 49 could be used, and in that event packing47 would not be needed.

A valve closure including a valve closure member 24 and a valve closureseat 28 is connected to the housing 12. The valve closure member 24 ispivotable from a closed position, in which it is seated against thevalve closure seat 28 and the flow passage 14 is blocked from the flowof produced fluid from the tubing string bore into the flow passage 14,to an open position in which the valve is open. The valve closure member24 is mounted on a pivot 26 and is biased to the closed position by apivot spring 27. In this preferred embodiment, the valve closure member24 is a flapper. However, the valve closure may be a rotating ball or asliding seal, both of which are commercially available.

A generally tubular actuator 39 for opening the valve closure iscoaxially mounted in the housing 12 and is movable from a firstposition, in which the valve closure member 24 is in its closedposition, to a second position in which the valve closure member 24 isin its open position and, as shown in FIG. 4, the end 41 of the actuator39 extends through the valve closure seat 28, so that the valve closuremember 24 is positioned in the recess 25 of the housing 12. As a result,the actuator 39 is adapted to protect the valve closure member 24 andthe valve closure seat 28 from the chemical fluid in the flow passage 14because the valve closure member 24 and seat 28 are effectively isolatedfrom the flow of chemical fluid in the flow passage 14. In thisembodiment, the actuator 39 is adapted to protect the valve closure.However, any suitable shield located in the housing 12 which is adaptedto move in response to the pressure of the chemical fluid upstream ofthe flow restrictor 22 may be used to protect the valve closure from thechemical fluid.

FIG. 7 shows piston unit 30 which is located in the housing 12. Pistonunit 30 has at least one piston 34 which is adapted for movement withinthe piston bore 32. FIG. 7 shows a piston unit 30 which has threesubstantially identical pistons 34. Referring to FIGS. 3 and 4, one ofthe three pistons 34 is shown. The pistons 34 are connected to theactuator 39 and are adapted to move the actuator 39 from its firstposition to its second position, in which the valve 10 is open, inresponse to the pressure of the chemical fluid upstream of a flowrestrictor 22 (which is described below). Each piston 34 is movablymounted in a piston bore 32 in the housing 12 that communicates with theopening in the housing 20 for fluid communication with the chemicalfluid source. Seals 33, which may be o-rings, packing, metal to metalseals or any other suitable material, reduce or prevent leakage aroundthe pistons 34. Each piston 34 is movable generally coaxially with theflow passage 14 and is adapted for longitudinal movement in each pistonbore 32 in response to the pressure of the chemical fluid upstream ofthe flow restrictor 22. The end of each piston 34 may be threaded toreceive a lug 35 with a lip 36 for engaging an annular groove 37 in acollar 38 that is connected to the actuator 39. A spring 44 urges thecollar 38 upward to move the actuator 39 to its first position, whereinthe valve is closed. The actuator 39 and the pistons 34 could be biasedupward using compressed gas in place of the spring 44, as is well knownto those skilled in the art. Compressed nitrogen is often used for sucha purpose. Furthermore, one annular piston (not shown) around theactuator 39 could be used in place of pistons 34. However, pistons 34are preferred when using the chemical injection valve in deep wells. Thecolumn of fluid acting on the surface area of a piston is greater indeep wells than in shallow wells. Because such an annular piston has alarger surface area than the combined surface areas of pistons 34, thedownward force acting on an annular piston is greater than that actingon pistons 34. And as a result, a disproportionately large spring 44could be required to urge the annular piston and thus the actuator totheir positions wherein the valve is closed. In more shallow wells, theeffect of the large surface area of an annular piston can be practicallycompensated for by a spring 44.

A flow restrictor 22 is located in the housing 12. The flow restrictor22 restricts flow of the chemical fluid through the flow passage 14 andthereby creates a pressure differential across the flow restrictor 22.This pressure differential results in a greater pressure in the flowpassage 14 than would exist without the flow restrictor 22. The flowrestrictor 22 of the preferred embodiment is an orifice plate having anopening therethrough which is sized to restrict flow of the chemicalfluid through the flow passage 14 and is connected to the housing 12downstream of the valve closure member 24. The opening through theorifice plate 22 should be no smaller than approximately 0.125 inches,otherwise solids may clog the valve. The preferred material for theorifice plate 22 is Tungsten Carbide which is resistant to wear anderosion. However, other materials which are resistant to wear andcorrosion may be used.

The orifice plate may be connected to the housing 12 or the actuator 39in the flow passage 14 at any point between the opening through thehousing 20 and the open end 18 of the flow passage 14, and the orificeplate will perform the same functions as described herein. However, theembodiment where the orifice plate 22 is connected to the housing 12downstream of the valve closure member 24 is preferred because, in thatlocation, the orifice plate will be relatively easy to remove withoutdisassembling the valve 10.

Referring to FIG. 3, to initiate injection of chemical fluid into thetubing string bore, the pressure of the chemical fluid source isincreased a predetermined amount such that the pressure of the chemicalfluid upstream of the flow restrictor 22 acting on the pistons 34 willovercome the opposing force exerted by the spring 44, and as a result,the pistons 34 will move downward in the piston bores 32. As the pistons34 move downward, the actuator 39 will also be moved downward by thecollar 38 connected to the ends of the pistons 34 by lugs 35. As theactuator 39 moves downward, it pivots the valve closure member 24 fromits closed position to its open position. The actuator 39 is preventedfrom further downward movement when the downwardly facing annular lip 45on the actuator 39 contacts an upwardly facing actuator seat 46. Thevalve is thereby opened, permitting communication between the flowpassage 14 and the tubing string bore, and the actuator 39 is in aposition wherein it will protect the valve closure from the chemicalfluid in the tubing string bore.

If the valve 10 does not have a flow restrictor 22, the pressure of thechemical fluid will decrease below its initial value when the valve 10is opened and the chemical fluid is injected into the tubing stringbore. The flow restrictor 22 is sized to restrict the flow of thecontinued supply of chemical fluid through the flow passage 14 in orderto create a pressure differential across the flow restrictor 22. Thispressure differential results in sufficient available pressure in thechemical fluid upstream of the flow restrictor 22 to act on the pistons34 and hold the actuator 39 in its second position, in which the valveis open, thereby continuing injection of the chemical fluid into thetubing string bore.

To close the chemical injection valve 10, the supply of pressurizedchemical fluid to the opening in the housing 20, and thus flow passage14, is decreased such that the force exerted on the pistons 34 by thespring bias 44 is greater than the pressure of the chemical fluidupstream of the flow restrictor 22 which is acting on the pistons 34.When this occurs, the spring 44 urges the collar 38, and therefore theactuator 39 and the pistons 34, upward in the piston bores 32. Asactuator 39 moves upward, valve closure member 24, which is biased toits closed position by pivot spring 27, will move to its closed positionagainst valve closure seat 28, as shown in FIG. 3, and block flow ofproduced fluid from the tubing string bore into the flow passage 14 andthus into the chemical fluid source.

FIGS. 5 and 6 show another embodiment of the present invention. Thischemical injection valve 10 has the same parts and is opened in the samemanner as the previously described embodiment. However, the actuator 39is connected to the flow restrictor 22 in addition to the pistons 34,and the flow restrictor 22 is adapted to hold the actuator 39 in itssecond position in response to the pressure of the chemical fluidupstream of the flow restrictor 22. As with the previous embodiment, ifthe valve 10 does not have a flow restrictor 22, the pressure of thechemical fluid decreases below its initial valve when the valve 10 hasbeen opened. Again, the flow of chemical fluid through the flow passage14 is restricted by the flow restrictor 22, and a pressure differentialacross the flow restrictor 22 results. However, in this embodiment, thispressure differential results in sufficient available pressure in thechemical fluid upstream of the flow restrictor 22 to act, not only onthe pistons 34 as described in the previous embodiment, but also on theflow restrictor 22 to hold the actuator 39 in its second position andthe valve 10 in the open position.

As described above, the pistons 34 and the flow restrictor 22 are allattached to the actuator 39. It should be noted that a chemicalinjection valve (not shown) having a flow restrictor connected to anactuator, but not to a piston, could be opened and maintained in an openposition by the pressure of the chemical fluid acting solely on the flowrestrictor. However, as the flow rate of the chemical fluid fluctuates,the valve closure member may not remain fully open, but may fluctuatebetween an open and a closed position because the pressure of thechemical fluid acting on the flow restrictor alone may not create agreat enough force to hold the valve closure member in a fully openposition. If, as described in the above preferred embodiment, thepistons 34 and the flow restrictor 22 are all attached to the actuator39, the pressure of the chemical fluid acting on the pistons 34 and theflow restrictor 22 creates a large enough force to decrease thisfluctuation. As a result, there will be less wear on the valve 10 whichwill extend the service life of the valve 10.

Referring to FIGS. 5 and 6, to close the chemical injection valve 10,the supply of pressurized chemical fluid to the opening in the housing20, and thus flow passage 14, is decreased such that the force exertedon the pistons 34 by the spring 44 is greater than the pressure of thechemical fluid upstream of the flow restrictor 22 which is acting on thepistons 34 and on the flow restrictor 22. When this occurs, the spring44 will urge the pistons 34, and therefore the actuator 39 and the flowrestrictor 22, upward in the piston bores 32. As the actuator 39 movesupward, the valve closure member 24, which is biased to its closedposition by the pivot spring 27, will move to its closed positionagainst the valve closure seat 28, as shown in FIG. 5. In this closedposition, the valve closure member 24 blocks flow of produced fluid fromthe tubing string bore into the flow passage 14 and thus into thechemical fluid source.

Having described specific embodiments of the present invention, it willbe understood that certain modifications thereof may be suggested tothose skilled in the art and it is intended to cover all suchmodifications as fall within the scope of the Applicants' claims.

What we claim is:
 1. A valve for injecting chemical fluid from achemical fluid source into the bore of a tubing string of a well, thevalve comprising:a housing including a flow passage therein forcommunicating with the tubing string bore and an opening therethroughcommunicating with the flow passage and the chemical fluid source; avalve closure including a flapper seat connected to the housing and aflapper pivotally connected to the housing, wherein the flapper ismovable from a closed position to an open position wherein the valve isopen; an actuator in the housing for opening the valve closure andmovable from a first position, wherein the valve closure is closed; to asecond position wherein the valve closure is open; a flow restrictor inthe flow passage, connected to the housing, for creating a pressuredifferential across the flow restrictor; and at least one pistonconnected to the actuator, in communication with the fluid sourceupstream of the flow restrictor, and adapted to move the actuator fromits first position to its second position in response to the pressure ofthe chemical fluid upstream of the flow restrictor; whereby the pressuredifferential across the flow restrictor results in sufficient availablepressure in the chemical fluid upstream of the flow restrictor to causethe piston to hold the valve open.
 2. The injection valve of claim 1further comprising: a shield in the housing adapted to move in responseto the pressure of the chemical fluid upstream of the flow restrictor toa position wherein it protects the valve closure from the chemicalfluid.
 3. A valve as defined in claim 1 wherein the flow restrictor isconnected to the housing downstream of the valve closure.
 4. A valve asdefined in claim 2 wherein the actuator and the shield are integral andadapted to move the valve closure to its open position in response tothe pressure of the chemical fluid upstream of the flow restrictor andadapted to shield the valve closure from the fluid.
 5. A valve forinjecting chemical fluid from a chemical fluid source into the bore of atubing string of a well, the valve comprising:a housing including a flowpassage therein for communicating with the tubing string bore and anopening therethrough communicating with the flow passage and thechemical fluid source; a valve closure including a flapper seatconnected to the housing and a flapper pivotally connected to thehousing wherein the flapper is movable from a closed position, whereinthe flapper is adapted to block flow from the tubing string bore, to anopen position wherein the valve is open; an actuator movable in thehousing for opening the valve closure and movable from a first position,wherein the flapper is in its closed position, to a second position,wherein the flapper is in its open position and adapted to protect theflapper and the flapper seat from the chemical fluid in the flowpassage; a flow restrictor connected to the housing for creating apressure differential across the flow restrictor; and at least onepiston in the housing, connected to the actuator, in communication withthe chemical fluid source upstream of the flow restrictor, and adaptedto move the actuator from its first position to its second position inresponse to the pressure of the chemical fluid upstream of the flowrestrictor; whereby the pressure differential across the flow restrictorresults in sufficient available pressure in the chemical fluid upstreamof the flow restrictor to cause the piston to hold the valve open.
 6. Avalve as defined in claim 5 wherein the flow restrictor is connected tothe housing downstream of the valve closure.
 7. A valve as defined inclaim 5 wherein the flow restrictor is an orifice plate having anopening therethrough sized to restrict flow of the chemical fluidthrough the flow passage for creating a pressure differential across theorifice plate.
 8. A chemical injection valve for injecting chemicalfluid from a chemical fluid source into the bore of a tubing string of awell, the chemical injection valve comprising:a tubular housing adaptedto be mounted to a mandrel in the tubing string, the housing including aflow passage therein having a closed end and an open end communicatingwith the tubing string bore, an opening therethrough communicating withthe flow passage and the chemical fluid source, and at least one pistonbore therein generally coaxial with the housing; a valve closureincluding a flapper seat connected to the housing and a flapperpivotally connected to the housing wherein the flapper is movable from aclosed position, in which it is seated against the flapper seat and theflow passage is blocked from flow of produced fluid from the tubingstring bore into the flow passage, to an open position wherein the valveis open; an actuator tube generally coaxial with the flow passage foropening the valve closure and longitudinally movable from a firstposition, wherein the flapper is in its closed position, to a secondposition, wherein the flapper is in its open position, and adapted toshield the flapper and the flapper seat from the chemical fluid in theflow passage; an orifice plate, connected to the housing in the flowpassage between the opening through the housing and the open end of theflow passage, the orifice plate having an opening therethrough sized torestrict flow of the chemical fluid through the flow passage forcreating a pressure differential across the flow restrictor; and atleast one piston in the housing generally coaxial with the flow passageand adapted for longitudinal movement in the piston bore, and connectedto the actuator tube, the piston in communication with the opening inthe housing for fluid communication with the chemical fluid sourceupstream of the orifice plate and adapted to move the actuator tube fromits first position to its second position in response to the pressure ofthe chemical fluid upstream of the orifice plate; whereby the pressuredifferential across the orifice plate results in sufficient availablepressure in the chemical fluid upstream of the orifice plate to act onthe piston and thereby hold the valve open.
 9. A chemical injectionvalve as defined in claim 8 further comprising a spring for biasing theactuator tube to its first position wherein the flapper is in its closedposition.